Reasons for lvl 6 12 man raid
1. It would be different than any other quest up to that point in the fact that it would allow 12 people a chance to play the same quest at the same time together. That is unique. Like TS is now (though you may not see TS runs, they crop up with startling regularity on Khyber).
2. Fun - sometimes it is just fun to kill things, very little would need to be changed with the quest as it is now for level 6, in fact because of how hard the final wave is, it might actually NOT need to be tweeked, 12 could handle it much better than 6 which might mean it would actually be MORE fun with 12 people.
3. Lowbies - there are some people who just like running the lowbie quests better, I know there are certain quests I *must* do when I am leveling a new character. Some of these are for the good XP, some are for usefull loot, some are to test weather the character build is actually going to be able to do what I want it to do (paper vs live). Powergamers could short man this for challenge, noobs could get into a big quest where the hardest part is staying alive & killing stuff -
4. Teamwork - you can't start training this too early - shroud 2 is a great example. I have been in groups that have great portal & harry beaters, but struggle on part 2 because they don't work well as a team. Simply having a quest where stuff spawns in a small room and needs to get beat down will help train new clerics on how to heal multiple battles, teach casters about crowd control, ect. Working together makes the quest easier, if people focus on killing something it will die faster & it is more obvious with 12 people hitting it than 6
The loot, while important, is actually irrelevant to weather we could USE a lvl 6 raid. Same with flagging, it is a red herring. The quest itself is either a valid idea or not - the details behind the rewards and how often you can play it have no bearing on weather the idea of a level 6 raid is worthwhile, only weather a PARTICULAR level 6 raid is worthwhile.
I personally think that by level 6 a character build is starting to have an idea of his/her place in a party. This could help a player with understanding that. I think that Kobold Assault was mentioned as a quest that people don't like, but I think in reviewing it that no one really likes it because it is long, the area is too big, there is no chest/loot worth anything, end reward stinks, & the only thing worth while is the favor, but if you don't have anyone to open it & you wan to do it at level, that is 3 runs at low levels, yeah it can be annoying.... This Devil's idea would not have that same problem as if you want hard or elite you would be a higher level...
Imp - I like the idea, don't quite see eye to eye on the rewards, but I am sure many people would disagree on many of the rewards that are already in the game, so not a big surprise. I think it would be a valuable addition to the game for the reasons listed above.